Mechanically-driven percussive tool



March 30 1926. 1,578,275 R. w.. J. FLETCHER Y MECHANICALLY DRIVEN PERCUSSIVE TOOL Filed Dec. 4, 1924 Driven Percussive Tools,

Patented Mar. 30, 1926; I

UNITED STATES PATENT OFFI E.

ROBERT WILLIAM JOHNSTON FLETCHER, OF EDINBURGH, SQOTLAN D.

MEOHLNICALLY-DRIVEN PEROUSSIVE TOOL.

- Application filed December 4, 1924. Serial No. 754,001,

To all whom it may concern Be it known that I, ROBERT WILLIAM x JOHNSTON FLETCHER,- a subject of the King of England, residing at Edinburgh, Midlo- Scotland, have invented certain new in 'Mechanically-- thian, and useful Improvements of which the following is a specification;

This invention is for improvements in or relating to mechanically driven percussive tools of the type comprising azrot'ary driving member, a spring-controlled reciprocating driven member and an operative connectionbetween the rotary driving and reciprocating driven members, a cam element and a co-operating abutment element in operat ve engagement with each other, one of which elements is rotated by said driving member and one of which is moved relatively to the other to reciprocate the driven member.

The invention has for one of its objects to improve tools of this type and to produce a construction which is simple to manufacture and efficient in operation. Another object is to convert some or all of the friction between the cam and its abutment to rolling friction, at the same time permitting the reciprocating member to have a sharp unhindered working stroke. It is also an object of the invention to overcome difficulties hitherto caused by the inertia of moving parts and render it possible always to keep the tool-bit incontact with the work. It is an additional object of the invention to provide an improved construction of mechanism for converting rotary into reciprocatory a high speed with a rapid snap action of the reciprocated member.

For a more complete understanding. of the invention there will now be described, by

way of example only and with reference to the accompanying drawings, one constructional form of percussive tool according to the invention; It is to'be understood, however, that the invention is not restricted to I the precise constructional details set forth.

In these drawings i Figure 1 is a longitudinal section through the tool, showing the parts in working posi- 1 tion;

Figure 2 is a like view showing the driving clutch disengaged. 1

Figure 3 is a perspective detail view of the operating cam, and

motion which can be operated atshaft casing not shown.

Figure 4 is a similar view of; a detail of i the tool which co-operates with the cam.

Like reference numerals indicate like parts throughout the drawings.

The tool body'or casing 10 ,is of tubular formation having a-n enlarged end 11. Its

other end is bored to receive a holder 12 for the t ool-bit.' This holder is retained in position by a detachable cap 13 and item be arranged to receive any desired form of tool-bit such as a hammer head,..chisel ,or

other implement chosen according to the work, such for instance as stone dressing, to be performed by the tool. A clearance is shown at 14 and it will be understood that consequently the holder 12 is permitted to take a certain amount of endwise movement inside the tool body 10. Its upward movement, however, is limited by the shoulder 15 and its downward movement by the cap 13. lVhen the tool-bit is held pressed against the work, the upper face 16 of the holder 12 willstand above the "face 17 inthe tool body and in this way thholder is adapted to serve as an; anvil to sustain blows from a reciprocator driven member 18. Theupper face 16 o the holder need 1 only project a very slight distance, above the face 17 so that the latter can be arranged to exert a. positive stop to the down-. Ward movement of the member 18 after the blow has been struck and the holder 12 consequently caused to Withdraw belowthe face 17. r

The enlarged end 11 of the tool body is received inside the hollow end 19 of a handle 20 which extcnds'in axial alignment end a socket 21 for connecting to a flexible The overlapping parts 11 and 19 are connected together by screws 22 in the tool body and washer plates 23 around the heads of the screws working.

in elongated slots 2 L in the hollow end of the handle. These slots permit the handle to have acertain amount of movement longitudinally of thetool body. -Mounted within the interior of the handle is a spindle 25 whereof theend: 26 is intended to be connected to the flexible shaft whereof the easing is received in the socket 21. The other end of the spindle 25 is engaged by a ball 27 which is pressed b a spring 28 in such a direction as to ten to push the handle with the. tool body and has atits further alongthe tool body in theopposite direci the handle to hold the tool against the work. When suchpressure is being applied the clutch by hand the pressure of the spring 28 will be overcome, but as soon as the hand pressure is relaxed the spring 28' will function to move the handle relatively to the tool as just described. 7 y

The relative longitudinal movement of the handle and tool body is utilized to cause engagement and disengagement between the two parts of adog clutch.- One of .these parts, namely the part 29 is carried on the spindle 25 against a bearing 30, and this part.

29 is the driving member of the clutch. The other-part 31 of the clutch is carried in a bearing in the tool body which will be described below, and the interior of the clutch part 31 is utilized to house the lower end 32 of the spindle 25, this being the end against which the ball 27 is pressed. From the foregoin it will be understood that when the tool isbeing ressed' against the work, the parts of the c utchwill be brought into engagement with each other, but when such pressure is relaxed, the spring 28 will move parts out of engagement with each other.

The enlarged end 11 of the tool body has its mouth closed by a cap 33 which is recessed toreceive a bearing 34, and passing I concentrically through this hearing is an em I tension 35 from the clutch part 31. This extension 35- houses the spring 28 and it constitutes the rotary driving member referred to at the commencement of this specification. It's; lower end is received within-the'interior of the upper. end of the reciprocating member 18 and is splined to the latter, as at 36, so that the member 18'will partake of its rotary movement while being free to reciprocate. 7 I v i y The reciprocating member 18 takes the form of a hollow sleeve with a closed lower end which reaches down into the interior of the smaller part of the tool body 10. In the interior of the sleeve is situated a control-, ling spring 37 which is the propelling medium causing the sleeve to strike the holder 12. The spring is received between the closed lower end ofthe reciprocating member 18 and the lower end 38 of the extension 35 of the clutch part 31 and is preferably permanently in compression. The upper end of the reciprocating member 18 has an external enlargement 39 constituting .acam element the lowerface of which is formed as a cam surface annularly arranged about the axis of the tool body. This cam surface is directed towards a co-operating abutment element constituted by a shoulder 40 in the interior of the tool body. Asthe parts rotate,

the efiect of the cam is to cause the reciproeating member 18 to be intermittently drawn away from the holder 12, thereby intermittently compressing the spring 37 and releas ing it so as to cause the member 18 to strike the holder 12. The cam surface ma conveniently have two downwardly directed hampered. The abutment 40 carries a ring I 43 which .is formed with two pockets for balls 44 situated at opposite ends of a diameter. The pockets are illustrated in detail in Figure 4 and it will be seen that one of the balls 44 has been omittted from that figure for the sake of clearness. In the c0nstruotion illustrated each pocket comprises an outer'wall 45 and an inner wall 46, these walls being concentric with the axis of the tool. body and the adjacent faces in each pair of walls are of concave formation, as at 47 to correspond with the shape of the balls 44. The. concave formation does not extend completely throughout the length of the walls 45 and 46, but shoulders 48 constituting stops. arelformed at one end of each pocket. The concave formation, however,

so a

extendscornpletely to the other ends of the pockets, and near these latter ends, stops in the form of studs 49 are fitted in the ring 43. 3 Each ball 44, therefore, can roll in its pocket between the two. concave faces, its

progress at the one end being limited by the 'stop 49 and'at the other end by the shoulders pockets merely by engagement with the surface of the'cam which, it will be appreciated,

is drawn towards the balls by the pressure of the spring 37. Referring now to Figure 3, the gradually sloping faces,offlth e cam are shown as being provided with grooves 50 to correspond to a portion of the contour of the balls 44, and the abruptly sloping faces of the camwith' corresponding grooves 51'. The halls are thus permitted a controlled translatory movement between the cam 39 and the ring 43 relatively to the driving member 35 and the driven member 18 in the same direction asvand also in the opposite direction to that of the rotary movement of the cam 39.

In operation, the spindle 25 with the clutch part 29 will rotate idlv until the operator presses the tool against the work.

This will cause the. two clutch parts 29 and I 31 to engage each other whereupon the rotation of the spindle 25 will be communicated to the cam. The ring 43 carrying the balls 44 is stationary and-consequently as the peaks of the cam ride over the balls the, member 18 will be reciprocated. It will be slowly drawn back away from the tool-bit holder 12 and allowed abruptly to move .to-

be the same.

It is, of course, not essential to employ two balls .nor to employ a cam with two peaks as any suitableliumber maybe'employed. Similarly, rollers may be substituted for balls and instead of the ball being carried in a pocket on the face of a flat abutment it could be carried by the cam. The cam may be detachable so as to be readily replaceable and the controlling spring for the reciprocating member may encircle it instead of being housed in its interior. The balls or rollers may be carried by-the reciprocating member and the cam afiixed to the body of thetool or the reciprocating member 'may have axial movement only and the cam or eooperating abutment may be arranged to be rotated. The construction may also be modified in other ways without departing from i the spirit and scope of the invention.

I claim 2-- v 1. In a tool of the character described, the combination of a casing, a rotatable driving member journaled therein, a reciprocatory driven member capable of longitudinal movement in the caslng, a cam e ementand element, and stops a cooperating abutment element, an antifriction bearing member between the said elements, one of which elements is rotatable in relation to the other and is arranged to be rotated by said driving member, and one is arranged to move in a direction towards and away from the other and to reciprocate said driven member, which bearing member is permitted a controlled translatory movement between said elements relatively to said driving 'and'driven members in the same direction as and also in the opposite direction to that of the rotary movement of themovable xed on one of said elements and arranged to limit the movement of said bearing member in' each direction of travel whilst permitting it to move bodily between the stops in relation to said elements, substantially as described. 1

2. In a tool of the character described, the combination of a casing, a rotatable driving member journaled therein, a reciprocatory driven member capable of longitudinal movement in the casing, a cam element and a cooperating abutment element, an antifriction bearing member between thesaid ele-' ments, one of which elements ,is rotatable in relation to the other and is arranged to be rotated by said drivingmember, and one is arranged to inove in a direction towards and way from the other and to reciprocate said driven member, a pocket of elongated part-circular shape in the face of said abutigient element for receiving said bearing memer, and arranged to limit the movement of said bearing member in said pocket in each direction of travel whilst permitting it to move bodily between the stops in relation to said elements, substantially as described.

3. In a tool of the character described, the combination of a casing, a rotatable driving member journaled therein, a reciprocatory driven member arranged to be rotated by the driving member and to move longitudinally relatively thereto, a cam element carried by said driven member and a cooperating abutment element fixed on the casing, a spring acting on said driven member and tending to press the cam element against said abutment element, balls between said elements, which balls are permitted a controlled transand stops fixed on the abutment element a latory movement about the axis of rotation of said cam element, and a plurality of stops,

two for each ball, fixed on said abutment element and arranged to limit'the movement of said ballsin each direction whilst permit- ;ting each ball to move bodily between its two stops in relation to said elements, which stops are so arranged as to ever. the driven member the action of its spring the relative position of said cam element, balls and abutment element shall always be the same, substantially as described.

4. In mechanism for converting rotary into reciprocatory motion, the combination of a cam element and a cooperating abutment element, whereof one is rotatable in reensure that when- 1s1mpelled under lation to the other and one is arranged to reciprocate in a directiontowards and away from the other, anti-friction bearing members. between said elements, which bearing members are permitteda controlled translatory movement about the axis of rotation of the rotatable element, and stops fixed on said abutment element and arranged to limit the movement of said bearing members in 'each direction of travel whilst permitting them to move bodily each between two stops in relation to said elements, driving means for rotatl'ng'the rotatable element, and a driven member arranged to be reciprocated by the reciiprocatory element, substantially as describe v i -In testimony whereof I aflix my signature.

ROBERT WILLIAM JOHNSTON l-hli'l'CilliR. 

